Chain grate



April 29, 1930. w. M. DUNCAN- CHAIN GRATE Filed April 2. 1928' 541mg mm;

Patented Apr. 29, 1930 PATENT OFFI CE WILLIAM M. DUNCAN, OF ALTON, ILLINOIS CHAIN Application filed April 2,

My invention relates to improvements 1n chain grates, the main object being to producea grate of this kind having its links reinforced by members stronger than the bodies of the links, in order to absorb the shocks and'tensile strain incident to the operation of the grate and to hold the parts of a link together in the event of fracture of the body of the link.

Linksfor chain grates must be constructed ofa material able to endure the abrasion from, and weight of, the fuel on the grate. The linkmust also endure the heat from the burning fuel, and the changes in temperature due to the passage of the link from the heated upper run of the grate in the region of the burning fuel to the cooler region of the lower run of'the grate.

For the foregoing reasons, chain grate links have, prior to my invention, been constructed of cast iron. The cast iron link must also endure the tensile strain placed upon it by the operation of the grate, during which'the chains comprising the grate are 95 pulled along under and with the fuel bed,

power being applied at one end of the grate and the pull transmitted from link to link through the pivot rods of the grate.

As is well known, cast iron is crystalline,

hard and comparatively inelastic, and is easily fractured by tensile strains and shocks,

I and a cast iron chain grate link in service very often does break in this manner.

An object of my invention is to reinforce a cast iron chain grate link to resist the tensile strains and shocks that the link is subjected to in service.-

The reinforcing member is preferably in- F terlocked with various portions of the cast iron link so that in the event of breakage of the cast iron, the link will not fall apart. The reinforcing member will unite the broken parts and permit the grate to con- F tinue in service, without incurring the risk of serious damage which has heretofore occurred when a broken link is passed around the sprocket wheels or over other elements of the structure which are likely to obstruct and hold a broken link.

According to one form of invention, the

GRATE 1928. Serial No. 266,521.

cast iron link has embedded therein an insert comprising a reinforcing member of a material better adapted to resist tensile strains and shocks than is cast iron.

This insert preferably comprises a steel bar within a cast iron link and bonded to the body of the link. The cast iron hubs of the link may contact with the pivot rods of the grate to reduce the friction there between, while the steel bar absorbs the shocks and carries a major portion of the tensile strain on the link from one pivot rod to the other. The reinforcing member also prevents the separation of parts of the link in the event of fracture.

With the foregoing and other objects in view, the invention comprises the novel construction, combination and arrangement of parts hereinafter more specifically described and illustrated in the accompanying drawings, wherein is shown the preferred embodiment of the invention. However, it is to be understood that the invention comprehends changes, variations and modifications which come within the scope of the claims hereunto appended.

Fig. 1 is a fragmentary longitudinal section of a chain grate embodying the features of this invention.

Fig. 2 is an enlarged detail side view of a chain grate link embodying my invention Fig. 3 is a sectional View along the line 3-3 of Fig. 2.

Fig. i is a perspective View of the insert.

To illustrate the invention, I have shown a supporting frame 1 provided with a hopper 2 for the discharge of fuel to a chain grate 3. The grate structure comprises many endless rows of grate links 4:, and pivot rods 5 connecting said grate links. The endless chains, produced by connecting the grate links, are fitted to a toothed drive wheel fixed to a shaft 7 (Fig. 1).

In the embodiment shown each of the links 4 comprises a cast iron body having a fuelsupporting longitudinal head 8, pivot-receiving hubs 9 at each end of said link, and a web member 10 depending from the head 8 to the bottom of the link and connecting the hub members 9. The lower portion of the cast web isdirectl'y between the hubs to receive the compresslve stresses transmitted from one pivot to the other. Baflie members 11 extend from the hub members 9 to the head 8 in order to prevent longitudinal leakage of air along the grate. (Fig. 2.)

A reinforcing member or insert 12 is embedded longitudinally and vertically medially in the web member 10 entirely below the fire in. the hub members 9 and the steel insert 12' hasapertures 14 registering with and exposed in the 'apertures13. The pivot rods 5 also extend through and contact with the walls of these apertures 14. v 1

The insert 12 has a plurality of approximately uniformly spaced openings 15, disposed around and between the hub members 9 and apertures 14. This insert is placed in the mold prior to the casting operation, and the cast. iron flows through the openings 15 to form bonding elements 16 connecting the opposite portions 17 of the web 10 and hubs 9. The insert 12 is thus interlocked with the web 10 and the hub members 9 of'the link (Fig. 8)

The cores in the mold (not shown) that core out the apertures 18-also extend through the apertures 14 during the casting of the link.

In use, thesteel pivot rods 5 contact with the cast iron walls of the apertures 13 of the hub members 9'to form a cast iron to steel bearing therebetween. This type ofbearingis best for' anunlubricated contact, such as is found in chain grate service.

The cast iron hub members 9 transmit the pull from one pivot rod through the bonding elements 16 around the hub to the steel insert 12 and thence in like manner to the next pivot rod. The bonding elements 16 intermediate the hubs prevent'local stresses in the cast iron web 10, and thus avoid cracking and breaking of the link through the web. These bond ng elements also tie the opposite ends of the l1nk 1. A chain grate link comprising a casting having a fuel supporting rib at the top, a web extending downwardly from said rib, and pivot receiving hubs integral with said web, the lower portion of the cast web being directly between said hubs to receive the compressive stresses transmitted-from one pivot to the other, and a tension member embedded in said cast web and connecting sa1d hubs to receiveithe tensilestresses transmitted from member consisting of a steel bar embeddedin said lower portion of the cast web and connecting said hubs to receive the tensile stresses transmitted from one. pivot to theother, said steel bar being entirely below said fuel-supporting rib.

In testimony that I claim the foregoing I hereunto affix my signature.

, WILLIAM M. DUNCAN.

together, so that if by accident the casting should be fractured, the link will not be broken apart,but may continue in service.

It will be readily seen, therefore, that I have provided a simple, inexpensive, and highly efficient means for preventing breakage of chain grate links due to tensile strains and shocks sustained by the link in the operation of the grate. 1 preferably do this by provid .ing a link of nonhomogeneousbut unitary structure, portions of the structure being well adapted to resist abrasive wear and compressive stress, and other portions being well adapted to resist tensile stress. 

